Control spring assembly for tractor hydraulic systems



CONTROL SPRING ASSEMBLY FOR TRACTOR HYDRAULIC SYSTEMS 3 Sheets-Sheet 1 Original Filed'Aug. 20, 1954 6 m R T 1 i wN W mw m V. w 1 3 .Q M l a K II R 0 M Ev W B y x fl a W a a, 2 Q \Q I &0 2N av N Q NM. \N 1% Q a. J a 8 w E 3 Q QWN J l, amN Q Q? Sept. 26, 1961 E. v. BUNTING 3,001,589

CONTROL SPRING ASSEMBLY FOR TRACTOR HYDRAULIC SYSTEMS Original Filed Aug. 20, 1954 3 Sheets-Sheet 2 IN VEN TOR. Emesl V. Bunting BY m, Am. 44%

Sept. 26, 1961 E. v. BUNTING CONTROL SPRING ASSEMBLY FOR TRACTOR HYDRAULIC SYSTEMS 5 Shets-Sheet 3 Original Filed Aug. 20, 1954 IN VEN TOR. Ernes t H Bunting F BY I AM; W

#fornew United States Patent 3,001,589 CONTROL SPRING ASSEMBLY FOR TRACTOR HYDRAULIC SYSTEMS Ernest V. Bunting, Detroit, Mich., assignor to Massey- 'Ferguson Inc, Racine, Wis., a corporation of Maryland Original application Aug. 20, 1954, Ser. No. 451,276. Divided and this application June 4, 1958, Ser. No.

4 Claims. (Cl. 1727) The invention relates to improved controls for hydraulic systems of the type provided in tractors for raising and lowering implements and for regulating their working depths. This application is a division of my copending application, Serial No. 451,276, filed August 20, 1954. V

' In tractor hydraulic systems of the above general character, regulation of the working depth is commonly effected by mechanism responsive to the soil reaction or draft load on the implement coupled to the tractor. The force generated by that load is transmitted to the tractor by way of the top link of the hitch linkage and the load is most conveniently measured by means of a control spring. In earlier installations of the type here under consideration, a control spring was used which acted only in compression as, for example, as shown in the Ferguson US. Patent, 2,118,180. As there described, soil reaction on the base of a plow or other implement attached to the hitch linkage tended to rock the implement forwardly about its pivotal connection to the lower draft links, therea 3,000 pound compression load.

by thrusting the top link forward; That forward thrust was applied as compression on the control spring in measuring draft load for automatic control purposes.

With attempts to use an ever-increasing scope of implements, it was found that some implements were of such light draft as compared to the rearward tilting tendency which they have due to their weight that even under full draft load they actually exerted a tension rather than a compression load on the top One solution to the problem thus presented is described and claimed in US. Patent 2,437,875 of John Chambers and the present inventor. In that patent, a double acting control spring installation is disclosed in which variations in eithertension or compression loading are utilized for control purposes.

One object of the present invention is to provide an improved control spring assembly'of the double acting type which eliminates certain objectionable characteristics of prior assemblies and makes it possible to utilize the full range of a double acting control spring.

Another object is to provide a control spring assembly which completely eliminates false cycling during transport and which retains its full operating range in all overload release settings.

Still another object is to provide a control spring assembly and linkage for transmitting controlling forces thereto which provides a true and accurate interpretation of the forces received from the implement under all conditions. 7

- A more specific object is to provide a linkage arrangement for transmitting forces to the control spring which minimizes its own intervention in the mechanical con nections and permits the top link and control spring to shift fore and aft without altering the effect of the link load on the spring by reason of changes in the link position.

Other objects and advantages of the invention will become apparent from the following detailed disclosure of the preferred embodiment illustrated in the accompanying drawings in which FIGURE 1 is a longitudinal sectional view through the Patented Sept. 26, 1961,

ice

center housing of a tractor equipped with a hydraulically elevatable implement bitch and control mechanism including a control spring assembly embodying the features of the invention. a

FIG. 2 is an exploded perspective view showing the manner in which the top link rocker and control plunger are interconnected for transmitting forces to the control spring.

FIG. 3 is a fragmentary sectional view showing the re: lationship between the control plunger and the top link in the upper and lower limit positions of the latter.

FIG. 4 is a stop motion sectional view showing the condition of the control spring assembly when subjected to a tension load of 1,000 pounds.

FIG. 5 is a view similar to FIG. 4 showing the condi: tion of the control spring assembly when subjected to FIG. 6 is a view similar to the preceding two figuresshowing the condition of the control spring assembly substantially at the point of the transition from tension to compression loading. v p

For purposes of illustration, a single preferred embodi ment of the invention has been shown and will be described herein in some detail. It is to be understood, however, that it is not intended that the detailed character of the disclosure should limit the invention to such particulars. The intention is to cover all equivalents and alternative arrangements falling within the spirit andv scope of the invention as it is more broadly and generally characterized in the appended claims.

The tractor selected to illustrate the invention has a center housing 10, which, together with the engine and gear box, constitute the backbone of the frameless tractor body. The exemplary tractor is provided with the usual front steering wheels and rear drive wheels. The latter are driven from the tractor engine through change-speed gearing by way of a power delivery shaft 12, a differ! ential 13 and axle shafts 14.

The exemplary tractor is equipped with a so-called three-point implement hitch familiar on Ferguson trac; tors and including a pair of lower or draft links 15 and. an upper or top iink 16. The draft links 15 are arranged in trailing relation to the tractor and to converge forward- 1y. At their forward ends these links are pivoted as at 20 on the rear portion of the tractor housing to swing vertically about a transverse horizontal axis located below and slightly forward of the axis of the axle shafts 14 for the tractor drive wheels. The pivots 29 permit lateral swinging of the draft links as well as vertical swing. Suitable coupling elements are provided at the rear ends of the links 15 and 6 for disengageable connection with any desired ground working or other implement to be coupled to the tractor. Top link 16 is connected to the implement structurein a manner such that forward tilting of the implement due to the soil reaction on its ground engaging parts is transmitted through the top link to a spring biased control plunger on the tractor to be described shortly.

Alongside the drivers seat is a hand control or quadrant lever 100. A hydraulic power mechanism controlled by this lever effects raising and lowering of the hitch linkage and such implement as may be carried. The hydraulic power mechanism or unit is powered from the tractor engine. It includes a hydraulic actuator which may be of any preferred form, that shown being a oneway ram comprising a cylinder 36 bolted or otherwise rigidly secured to the underside of a cover plate 26 for the tractor center housing. The cylinder opens to the rear and slidably receives a piston having a piston rod 38 projecting rearwardly therefrom. The ball-shaped outer end of the piston rod is received in the socketed lower end of an arm 39 rigid with a transverse rockshaft 40 accordance with the reaction.

Iver

journaled in the upper rear portion of the tractor body,

f The arrangement is such that when pressure fluid (such as oil) is'suppli-ed to the closed end of the cylinder 36, the. piston is forced rearwardly to rock the arms 41 upwardly and thus raise the lower draft links 15. Simi larly, upon exhaust of fluid from the cylinder, the piston 37 is permitted to retreat into the cylinder under ur ing of the gravity loads of the links 1.5- (and any implement attached to them) so that the links swing downward in a lowering direction. Y

The volumetric rate at which oil is supplied to or exhausted from the ram cylinder 36 will accordingly determine the rate at which the draft links 15 are raised or lowered; In the present instance, pressure fluid for operating the ram is supplied from a positive displacement pump 45 located in the center housing below the ram. ,The lower portion of the housing is flooded with oil constituting a sump for the system. Oil enters the pump through an intake passage cored in the pump body and is discharged from the pump through a conduit 48 leading to the closed end of the cylinder 36. A spring loaded safety valve 454: relieves the high pressure side of the pump when excessive pressure develops.

lathe-illustrative embodiment the pump 45 is driven through the tractor engine through a pump and power take-off shaft 46 independently of the change-speed transmission, although, of course, other drive connections are available. With the pump driven by an engine Whose speed must necessarily vary because of other demands made on it by the tractor, provision must be made for controlling the volumetric delivery rate of oil from the pump independently of pump speed. While various expedients for that general purpose are known in the art, the one employed here is to provide a control valve eflective to vary the amount of oil permitted to enter the pump, thereby varying the amount of oil delivered from it to the cylinder 36.

The control valve of the exemplary tractor is located in the lower portion of the pump housing. It includes a plunger 55 shiftable axially to meter fluid into or out of the hydraulic system to eifectively lock the fluid in the ram. The present invention is not concerned with the precise construction of this valve or with the particular mechanism or linkage by which it is shifted through its various positions. It is sufiicient to note at this point that two sources of control action are utilized for shifting the valveone manual, the other automatic. The automatic action drives from the soil reaction on the implement which is measured by a control spring assembly on the tractor, the force being applied to it through thetop link 16 of the hitch. The measured force is transmitted through a linearly movable control member herein shown as a push rod 131 passing beneath the 'rockshaft 4t) and displaced axially in proportion to soil reaction (draft load) on the implement. Such displacement is utilized to shift the valve'plunger in combinationwith the manually operable control'elernents including the'hand lever ran and a second quadrant lever or depth setter" designated generally at 141. For a detailed description of the construction and operation of this mechanism, reference may be had to the parent application.

As indicated above, the force generated by soil reaction on the implement is transmitted to the controls through the push rod 131 which is displaced axially in The control spring as herein shown is a heavy coil spring 29. In the present instance, it is enclosed within a hollow longitudinal rib or top extension 26a of the'center housing cover plate 26. This extension terminates at its rearward end in a bifurcatedportion presenting a pair of 'jaws 26b, (FIGS. 2 and 3). Between these jaws .is pivoted a rocker 25 4 on a pair of cap screws 24, one in each jaw, so that the rocker can swing freely on them fore and aft. The rocker is U-shaped, extending forwardly within the confines of the jaws and has two depending extensions 25a integral with its respective legs 25b, one on each side, and extending down from the pivot points aflordcd by the screws 24. Lying between the laterally ofiset lower depending portions of those legs 25a and extending forwardly from them is a U-shaped yoke 27. Registering holes in the legs of the rocker and the yoke respectively receive bushings 260 which pivotally connect the rocker and the yoke together. A removable coupling pin 21 inserted through the bushed holes serves to couple the 7 top link 16 to the assembly.

The construction provided by the invention permits the top link 16 of the hitch to be quickly and easily attached to or detached from the rocker 23 and yoke 27. To connect the link, its forward end, which is equipped with an apertured, swiveled ball 16a, is simply dropped into the opening between the jaws 26b and the pin 21 is inserted (through the holes in the rocker and yoke legs and the swiveled ball on the link). Disconnection is equally easy, requiring simply withdrawal of the pin and lifting up the top link 16. Being able to drop the link in from the top, the maneuvering of the tractor and the implement in efiecting-a coupling is simplified.

0n the forward portion of the yoke 27 is an integral tubular head 27a (FIG. 2) internally threaded to receive a control plunger 22 (FIGS. 1 and 3). After being threaded into the head 27a, the plunger is locked in place by a transverse pin 22a (FIG. 4). At its forward end the plunger 22 has a head 22b with a peripheral flange 22c slid'ably received within a cup 28. The latter is integrally flanged at its open end to define an abutment engageable by the flange 22c upon rearward movement of the plunger. The cup is, in turn, slidable endwise within a bore 31 in the housing.

The control spring 29 encircles the plunger 22. A colla- 30 (FIGS. 1 and 4-6) threaded in the housing forms a stop for the spring when the latter is drawn rearwardly. The spring is heavy enough so that its deflection under loads of order of magnitude encountered in that operation of the tractor shifts the. plunger only short dis tances. For example, in .one installation a spring was used having deflection from an unstressed condition of 0.1-3 inch with 1,000 pounds of tension load applied and 0.39 inch deflection with 3,000 pounds compression load as illustrated infIGS. 4, Sand 6.

The push rod 131 heretofore referred to as imparting control motion in the hydraulic system bears against the plunge head 22b. r d is gu di s y receive in p rtures in afl'ange on the housing cover plate 26 and in a closure plate 31;: at the inner end of the bore 31 A spring bias n the linkag through hich' e push od 131 acts urges the rod rearward into contact with the plunger head. Accordingly, as the plunger 22 moves forward or back under loading applied from the hitch, the push rod 131 will follow its motion and apply it to a rocker for determining the positionof the valve plunger 55.

In the operation of .aitractor equipped with a control h e as mbly of th type above described, re p n t soil reaction on the implement is continuous throughout a range embracing both tension and compression. Ihus, when the top link 16 is tensioned the rocker 25 tends to swing rearward anddraw the plunger 22 and cup rearward so that the spring 29 is compressed between the cup 28 and collar .3!) as shown in FIG. '4. Conversely, when compression .is applied to the top link, the rocker 25 tends to swing forward and thrust the plunger 22 forward so that the spring is compressed between the head 27a and the rearendof the cup 28, the latter cup having gone solid against the partitions 3111 (as shown in FIG. 5). The present installation has the advantage, however, that here for the first time it is possible to use a full range for such a double acting spring. Neither false cycling during transport nor overload release settings diminish the range by reason of the novel relation of the system components with the double acting spring.

In assembling the spring mechanism the cup 28 and spring 29 are slipped onto the plunger 22. The collar 30 is loosely strung on the yoke head. The plunger is then screwed into the yoke head 27a, being tightened down just sufliciently to eliminate end play. When so tightened, the locking pin 22a is inserted. Such parts are then slipped into the housing and the collar 30 screwed into place. The latter is screwed in with the depth setter 141 in its down position and just sufliciently to eliminate end play. A set screw (not shown) is then tightened to lock the collar 30 in place.

A cup shaped flexible rubber cover 32 may be provided to prevent entry of dirt and dust into the spring housing.

The rocker arrangement described is particularly suited for obtaining most favorable action of the control spring under a wide range of conditions. Heretofore it has been customary to mount a bell crank rocker at 21a (FIG. 1) with the rocker pinned to a control plunger at the juncture of its arms and the top link pivoted to the rear end of the trailing arm of the bell crank. During use the top link must swing up and down. When an implement is digging deeply, it is well below horizontal, as shown in full lines in FIG. 3, and in transport the top link is cocked upward from the horizontal as shown in broken lines in that figure.

With such previous form of rocker the rocker itself interposes substantial changes in the forces transmitted to the control spring. When swung either above or below horizontal, the rocker itself multiplied the load applied to the spring and it increased the multiplication progressively as the top link swung further from horizontal. Faulty control action resulted since the rocker gave a false interpretation of the forces being transmitted through the link. For example, in heavy going when the tractor rear wheels slipped they tended to dig in. But that lowering of the tractor is reflected in the upward swing of the top link. Consequently, the bell crank rocker (having a lessened mechanical advantage over the spring) relayed a message of lesser draft load so the system tended to send the implement even deeper. Of course, that is the very opposite of what is required to help the tractor in that point.

The presently disclosed rocker arrangement has the virtue that it its own intervention in the mechanical connections. It permits the top link and control spring to shift fore and aft, yet it does little to alter the eiiect of link load on the spring with changes in link position. In the present arrangement, the connection point (21) for link to spring assembly is also the point of rocker connection to spring assembly so that no material alteration in the geometry of the connections results (see FIG. 3).

It will be apparent from the foregoing that the invention provides a spring assembly of novel and advantageous construction for the control of a tractor hydraulic system. Due to the novel relationship between the spring and the linkage utilized to transmit measured forces to the control valve, it is possible to utilize the full range of a double acting spring with its accompanying advantages such as the wider range of implements that can be accommodated on the tractor. Furthermore, the novel linkage arrangement by which the top link is connected to the control spring completely eliminates faulty control action due to changes in the geometry of the linkage. The spring assembly is efficient and reliable in operation, and in addition, materially simplifies the job of connecting and disconnecting the top link and in effecting the initial adjustments in the assembly of the tractor.

I claim as my invention:

1. In a tractor having a power lift mechanism for operating a hitch link, the combination of a control plunger supported on the tractor for axial movement, spring means interposed between a part of said tractor and said plunger yieldably resisting movement of the plunger, means for controlling the operation of said power lift mechanism, a linkage interposed between said controlling means and said plunger for actuating the controlling means in response to changes in stress applied to said plunger, and'means for applying stress to said plunger including a rocker supported in depending relation from a pivot on the tractor above one end of said plunger, a hitch link, and means for pivotally connecting said last mentioned hitch link, 21 depending portion of said rocker, and said plunger, all at a common pivot point, to thereby minimize variations, incident to vertical swing of such link, in stress applied by the latter to said plunger.

2. The combination with a tractor having a three-link implement bitch and a power unit for raising and lowering the hitch, a housing enclosing said power unit and having an access opening in its top wall, control mechanism for the power unit including an axially shiftable control plunger and a control spring assembly operative to resist movement of the plunger in either direction, a cover plate attachable to the housing in position to close said opening, a housing formed integral with said cover plate dimensioned to enclose said plunger and said control spring assembly and having means supporting and guiding the plunger in its axial movements, a pair of laterally spaced jaws integral with and extending rearwardly from said spring housing, a rocker pivotally suspended between said jaws, and means pivotally connecting one of the hitch links and said control plunger to said rocker at a point spaced below its pivot.

3. The combination with a tractor having a three-link trailing implement hitch and a power unit for raising and lowering the hitch, of a housing enclosing said power unit and having a pair of rearwardly projecting laterally spaced jaws, control means for the power unit, an axially shiftable plunger supported in said housing, a linkage connecting said plunger to said control means, a biasing spring interposed between said housing and said plunger resisting movement of the plunger in either direction, said plunger having one end portion projecting from the housing below said jaws, a U-shaped rocker dimensioned to fit between said jaws with its legs extending rearwardly, said rocker legs having extensions projecting downwardly and spaced apart to straddle the projecting end of said plunger, a U-sh-aped yoke fixed to the projecting end of the plunger and dimensioned to fit between the extended legs of said rocker, connecting elements pivotally connecting the legs of said rocker to the respective jaws, tubular connecting elements pivotally connecting the legs of the rocker with said yoke, the connecting elements at each side of said rocker being separate so as to leave a clear generally vertical passage through the rocker for insertion of one of the hitch links into operative relation with said yoke, and a pin insertable through said tubular connecting elements for pivotally connecting the rocker, the hitch link and the yoke together.

4. The combination with a tractor having a three-link trailing implement bitch and a power unit for raising and lowering the hitch, of a housing enclosing said power unit and having a pair of rearwardly projecting laterally spaced jaws, control means for the power unit, an axially Shiftable plunger supported in said housing and operatively connected with said control means, a spring interposed between said housing and said plunger resisting movement of the plunger, said plunger having one end portion projecting from the housing below said jaws, a U-shaped rocker dimensioned to fit between said jaws with its legs extending rearwardly, said rocker legs having extensions projecting downwardly and spaced apart to straddle the projecting end of said plunger, a U-shaped yoke fixed to the projecting end of the plunger and dimensioned to fit between the extended legs of said rocker, connecting elements pivotally connecting said rocker to v v I said ja s, to swing qye d t, ubu ar im in l== ma s onm in s id mm: and a' d Y9K? t pi e m an par l l to pi o 9 said mk r a cxtsm n t o h aid fibul dem fi il l as bly qonnwing one f h v hi nkswi h 5319 3'01 9 q p QL- a1 mq m about a co m n xi wi h a= d swk .said Pin being r a l to asc 11w link whik tha pi qtal nn o e e n he y ke and aid 9l$f mma m efiwt Keismscss ii d ihc fil 9; t i sea U T D ST S TENTS Klemm ct -,-"'-V-- '7: Senkomki et al. Mar. 26, 1957 FOREIGN PATENTS P am? m- 3 52 F anc Rb- :10; 1 4 

